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Technical Discussion » Bullet vs RBD solver: dynamic/prefractured objects.
- strafer
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Ahh I see, thanks for the response! I wasn't aware bullet did not take into account magnet forces for breaking glue. The result makes much more sense now.
Houdini Indie and Apprentice » display fracture object names in Geo SOP?
- strafer
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The option to display object names works well for objects that have been turned into dynamics, but I'd like to see piece names of an object that has been pre-fractured on the geometry level. Is there an easy way to see this?
-Thanks
-Thanks
Houdini Indie and Apprentice » Bullet solver and complex collision volume shapes
- strafer
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I'm curious how people are using Bullet in simulations. I'm noticing that with any complexity to the collision volume (i.e. any concave-ness) Bullet breaks down horribly and bounces off the volume like it was an implied cube.
How are people using Bullet to get around this problem? I'd really like to use Bullet for what I'm working on because it's so much faster but I'm not sure how to do something simple like create a wall with a few indents in it and have Bullet work with that shape.
Bullet is great against the default ground plane but against anything else it seems to be pure fail for me regardless of what settings I use.
How are people using Bullet to get around this problem? I'd really like to use Bullet for what I'm working on because it's so much faster but I'm not sure how to do something simple like create a wall with a few indents in it and have Bullet work with that shape.
Bullet is great against the default ground plane but against anything else it seems to be pure fail for me regardless of what settings I use.
Technical Discussion » Variable number of break SOPs?
- strafer
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In looking at it more I think I understand better now. Folder0 is the name of the multiparm list in the digital asset and the way your formula was setup gets us the names of xform1_r#x r#y and r#z. Seems like you used index stamp name instead of stamp name so you could start with 0 which is a better index to start with.
Technical Discussion » Variable number of break SOPs?
- strafer
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Awesome! Once I set the each node to merge mode I got what I was looking for perfectly.
I'm kind of curious about ch(“folder0”)-1, does that take the input into input #1 of the foreach inside my digital asset? I'm guessing you did a -1 since I was sending in a grid already, so the first object was already there.
I have a couple questions on the transform rotation formula you used. Why did you use FORIDXVALUE over FORVALUE as it appears they both work? Also stamps() instead of stamp()? In looking at the houdini help files it seems like stamps is used when retrieving a string? I guess I'm a little fuzzy on the conditions one would use FORIDXVALUE vs FORVALUE
Thanks for the help!
I'm kind of curious about ch(“folder0”)-1, does that take the input into input #1 of the foreach inside my digital asset? I'm guessing you did a -1 since I was sending in a grid already, so the first object was already there.
I have a couple questions on the transform rotation formula you used. Why did you use FORIDXVALUE over FORVALUE as it appears they both work? Also stamps() instead of stamp()? In looking at the houdini help files it seems like stamps is used when retrieving a string? I guess I'm a little fuzzy on the conditions one would use FORIDXVALUE vs FORVALUE
Thanks for the help!
Technical Discussion » Variable number of break SOPs?
- strafer
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Feel like a dummy because I'm sure I'm missing something ultra-simple but I can't seem to get this working. I dragged the rotation values into the type property>parameters of my asset but I'm not seeing any of the grids from my foreach node changing.
I can tell its creating multiple grids because when I MMB click over the digital asset and I see that I have 3 polygons when I set my foreach number to 3.
What am I missing here?
I can tell its creating multiple grids because when I MMB click over the digital asset and I see that I have 3 polygons when I set my foreach number to 3.
What am I missing here?
Technical Discussion » use opinput() in file node?
- strafer
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Technical Discussion » use opinput() in file node?
- strafer
- 12 posts
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I'd like to use the name of an input node as the filename for my file exporting. Any tips on this?
I've tried entering the expression opinput(“.”, 0) in the file path itself and also creating an attribute (type: string) as well with no luck.
I've tried entering the expression opinput(“.”, 0) in the file path itself and also creating an attribute (type: string) as well with no luck.
Technical Discussion » Variable number of break SOPs?
- strafer
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I'm trying to figure out a way for a digital asset to add a user defined set of break planes to an object but am stumped on where to look.
I've been following a bunch of Peter Quints tutorials on ForEach and noticed his last one was sort of close (http://vimeo.com/7361320 [vimeo.com]) but it uses cut planes and random numbers for rotations. What I'm looking for is a way to control the parameters of each Break SOP that I'm adding, but have the number of Breaks SOPS added controlled by an integer variable, so maybe I'll use 2, 5, 8, etc.
Does anyone know of a way to do this?
Thanks!
I've been following a bunch of Peter Quints tutorials on ForEach and noticed his last one was sort of close (http://vimeo.com/7361320 [vimeo.com]) but it uses cut planes and random numbers for rotations. What I'm looking for is a way to control the parameters of each Break SOP that I'm adding, but have the number of Breaks SOPS added controlled by an integer variable, so maybe I'll use 2, 5, 8, etc.
Does anyone know of a way to do this?
Thanks!
Technical Discussion » Bullet vs RBD solver: dynamic/prefractured objects.
- strafer
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Hello, I'm having some difficulty figuring out when I should use RBD or Bullet as a rigid body solver. I'm noticing that I get drastically different results depending on whether or not the object is pre-fractured or fractured dynamically. The fracturing parameters are identical for both the dynamic and pre-frac'd geometry.
With BULLET as I increase the metaball strength my cube simply flies higher on the pre-frac'd geometry. I don't understand why larger magnet forces pop the box up faster and don't shatter the pre-frac'd geometry. Bullet works fine on my dynamic fractured geometry however.
With RBD, it works as expected for dynamic but pre-frac ONLY works if I set ‘solver per object’ in the options. (Without solver-per, the box does not break at all and with my inner glue strength at 10 and my magnet force at 4000 one would think that it would break apart no matter what.)
Does anyone have any thoughts on why Bullet seems to work so oddly with pre-frac'd geom and why I need a solver per object?
Thanks!
With BULLET as I increase the metaball strength my cube simply flies higher on the pre-frac'd geometry. I don't understand why larger magnet forces pop the box up faster and don't shatter the pre-frac'd geometry. Bullet works fine on my dynamic fractured geometry however.
With RBD, it works as expected for dynamic but pre-frac ONLY works if I set ‘solver per object’ in the options. (Without solver-per, the box does not break at all and with my inner glue strength at 10 and my magnet force at 4000 one would think that it would break apart no matter what.)
Does anyone have any thoughts on why Bullet seems to work so oddly with pre-frac'd geom and why I need a solver per object?
Thanks!
Technical Discussion » Basic RBD shatter questions
- strafer
- 12 posts
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Thanks Manu! I had actually tried adjusting the density to 10 in a previous version, but it tended to leave the front of the column intact while blowing out the back of it. Mass = 10 is I'm guessing significantly less mass than when it's calculated auto when Density = 10.
In any case, when running simulations like this is the best practice not to worry about getting the density of the physical object correct and instead just worry about how it looks? I.E. if it was a concrete pillar it's not important that it's density be ~2000. Or is it best to use physically correct values and compensate in other areas? I had thought my solution would be to leave the pillar's density at the correct value for concrete and instead increase the values of the projectile object, its speed, density, mass, etc. but that did not seem to give me correct results either.
Seems like what would work best is a way for the projectile object not to be affected as much by the impacts on geometry and for it to mostly push other geometry out of the way, since it always seems to deflect off and not push through the object like I'd like it to.
In any case, when running simulations like this is the best practice not to worry about getting the density of the physical object correct and instead just worry about how it looks? I.E. if it was a concrete pillar it's not important that it's density be ~2000. Or is it best to use physically correct values and compensate in other areas? I had thought my solution would be to leave the pillar's density at the correct value for concrete and instead increase the values of the projectile object, its speed, density, mass, etc. but that did not seem to give me correct results either.
Seems like what would work best is a way for the projectile object not to be affected as much by the impacts on geometry and for it to mostly push other geometry out of the way, since it always seems to deflect off and not push through the object like I'd like it to.
Technical Discussion » Basic RBD shatter questions
- strafer
- 12 posts
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Hello, I've recently started learning about Houdini's fracture and RBD tools and have some questions on some of my early test work. I'm trying to figure out how to have a RBD object pass through a dynamic or pre-fractured column.
The main problem I'm having is that the RBD collision object seems to always bounce or get stuck instead of passing through the column and pushing the pieces out of the way. I've tried various combos of settings: (velocity transfer in the fractureparms, different densities, object collision speeds, stiffness/bounce/friction, glue strengths on my pre-fractured column, etc.) but am having no luck with anything I try.
It would seem to me that larger densities and higher speeds on the RBD object should get the result I want but no luck so far. I've tried lower densities on the column object as well, but it just seems to make the pieces in the back of the pillar opposite the impact point fly out faster, while the areas in the front of the column seem to collide together and fall downward. What settings am I missing here?
* files are made in Houdini master 11 non-commercial
The main problem I'm having is that the RBD collision object seems to always bounce or get stuck instead of passing through the column and pushing the pieces out of the way. I've tried various combos of settings: (velocity transfer in the fractureparms, different densities, object collision speeds, stiffness/bounce/friction, glue strengths on my pre-fractured column, etc.) but am having no luck with anything I try.
It would seem to me that larger densities and higher speeds on the RBD object should get the result I want but no luck so far. I've tried lower densities on the column object as well, but it just seems to make the pieces in the back of the pillar opposite the impact point fly out faster, while the areas in the front of the column seem to collide together and fall downward. What settings am I missing here?
* files are made in Houdini master 11 non-commercial
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